Known systems for treating exhaust gases passing through an exhaust system of a diesel engine include a diesel particulate filter (DPF) that traps diesel particulate matter (DPM).
A DPF requires regeneration from time to time in order to maintain particulate trapping efficiency. Regeneration involves creating conditions that will burn off trapped particulates whose unchecked accumulation would otherwise impair DPF effectiveness.
The creation of conditions for initiating and continuing regeneration generally involves elevating the temperature of exhaust gas entering the DPF to a suitably high temperature. Because a diesel engine typically runs relatively cool and lean, the post-injection of diesel fuel has been used as part of a DPF regeneration strategy to elevate exhaust gas temperatures entering the DPF while still leaving excess oxygen for burning the trapped particulate matter.
When a vehicle is being operated in a way conducive to DPF regeneration, such as cruising on a highway, the regeneration process may be conducted with little or no significant effect on vehicle driveability and may be initiated either by the driver or else automatically by a regeneration initiation strategy even before the DPF becomes loaded with DPM to an extent where forced regeneration would be mandated by the engine control system. Regeneration can even be initiated while a vehicle is parked, provided that engine operating conditions and the immediate surroundings are appropriate for regeneration.
The inventors have observed occurrences of fuel system cavitation during certain regeneration events. Cavitation is typically undesired in hydraulic systems, such as an engine's fuel injection system, because it can eventually lead to damage and ultimately component and/or system failures. Cavitation can also contribute to an engine manufacturer's warranty costs.
Their observance of occasional fuel system cavitation during DPF regeneration has led the inventors to seek a solution for mitigating, and ideally eliminating, such cavitation.